Tractors are used for performing a variety of tasks by attaching to the rear of the tractor a myriad of implements such as used for ploughing, cultivating and lifting. There are numerous implement designs for carrying out the desired tasks. More specifically, the lifting implements for tractors used to handle and lift heavy loads have been designed to attach to the three point hitch of a tractor. In other instance, the lifting implements are attached to the draw bar. However, the lifting implements having lifting arms or booms typically require an independent source of hydraulic power to raise and lower the lifting arm. Therefore, known hydraulic lifting implements are complex in structure and costly to purchase for the individual user or small farm owners. Moreover, the independent source of hydraulic power in some instance connects to the tractor's hydraulic system. Henceforth, the hydraulic lifting implements are not easily attached and detached to the tractor.
For example, U.S. Pat. No. 3,940,000, issued Feb. 24, 1976 to Mousel, entitled "UNIVERSAL HYDRAULIC LIFT ATTACHMENT FOR TRACTORS" discloses a hydraulic lift system having an independent piston detachably connected to the hydraulic system of a tractor. The frame is primarily supported by the tractor's draw bar.
U.S. Pat. No. 4,067,471, issued Jan. 10, 1978 to Roatcap, entitled "THREE POINT TRACTOR HITCH BOOM ATTACHMENT" discloses a tractor hitch boom attachment utilizing the conventional three point hitch mounting mechanism. The boom is rotated within an arc via an actuator means.
U.S. Pat. No. 5,129,7115, issued Jul. 14, 1992 to Coats et al., entitled "BALE HANDLING APPARATUS" discloses a bale handling apparatus for attaching to a tractor specifically for handling, moving, and manipulating large cylindrical hay hales.
U.S. Pat. No. 4,068,774, issued Jan. 17, 1978 to Howell, Jr., entitled "MATERIAL HANDLING IMPLEMENT" discloses an implement for carrying and handling materials mountable to a conventional tractor three point hitch.
U.S. Pat. No. 4,394,107, issued Jul. 19, 1983 to Siebert, entitled "TRACTOR MOUNTED FORKLIFT" discloses a forklift attachment for tractors having a three point hitch.
U.S. Pat. No. 4,345,871, issued Aug. 24, 1982 to Kalif, entitled "HIGH-LIFT ATTACHMENT FOR AN AGRICULTURAL TRACTOR PROVIDED WITH A THREE-POINT LINKAGE" discloses a tractor-lift attachment utilizing a platform and frame for mounting to a conventional three point tractor hitch.
While each of the above prior lifting device function as desired, none of the above device utilize both the tractor's three point hitch and the tractors draw bar wherein the tractor's draw bar is utilized to rotate the telescopic lifting arm via a pulley assembly. Furthermore, the above devices do not provide a hydraulic lift boom attachment having a support frame which includes a telescopic vertical support assembly to vary the vertical height of the telescopic lifting arm independent from the pivotal rotation to raise or lower the telescopic lifting arm.
As can be appreciated, the telescopic vertical support assembly in combination with the utilization of both the tractor's three point hitch and the tractors draw bar allows the overall vertical lifting height to be maximized while providing a hydraulic lift boom attachment which is sturdy and structurally relatively simple.
As will be seen more fully below, the present invention is substantially different in structure, methodology and approach from that of the prior hydraulic lift attachments.